1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium bromide monohydrate

In the title hydrated molecular salt, C11H14N3O+·Br−·H2O, the Br− anion is split and appears as two independent half-occupied Br− anions on twofold rotation axes. The dihedral angle between the phenyl ring and the mean plane of the 2,3-dihydro-1H-pyrazole ring (r.m.s. devation = 0.014 Å) is 62.43 (7)°. In the crystal, the components are connected via O—H⋯Br and N—H⋯O hydrogen bonds to form a one-dimensional polymeric structure propagating along [001].

supplementary materials Acta Cryst. (2012). E68, o1964 [doi:10.1107/S1600536812023550] 1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-aminium bromide monohydrate Yan-Yun Yang, Liang Xu, Ting-Guo Kang, Ting Chen and Ping Wu Comment 4-Aminoantipyrene, which contains a pyrazolone ring, is an important compound in the class of analgesic agents used in otic solutions in combination with other analgesics such as benzocaine and phenylephrine (Jain et al., 2003). Pyrazolone is a five-membered lactam ring compound containing two N atoms and a ketone in the same molecule. Such pyrazolone derivatives form a very important class of heterocycles due to their properties and applications (Casas et al., 2007;Zhang et al., 2008). We report herein on the synthesis and crystal structure of the title compound.
In the crystal, the various components are connected by N-H···O and O-H···Br hydrogen bonds (Table 1 and Fig. 2) to form an infinite one-dimensional arrangement parallel to [001].
Experimental 4-Aminoantipyrine (0.203 g, 1.0 mmol) and dibromomethane (0.173 g, 1.0 mmol) were dissolved in water (15 ml). The mixture was refluxed for 3 h and then the solvent was evaporated on rotary evaporator to almost dryness. The crude product was recrystallized from water yielding block-like yellow crystals of the title compound.

Refinement
The H atoms were included calculated positions and treated as riding atoms: (C,N,O), where x = 1.5 for CH 3 and NH 3 H atoms and = 1.2 for other H-atoms.

Computing details
Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998  The molecular structure of the title compound with the atom numbering. The displacement ellipsoids are drawn at the 30% probability level.

Figure 2
A view along the c axis of the crystal packing of the title compound. H-bonds are shown as dashed lines; see Table 1 for details. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.48 e Å −3 Δρ min = −0.40 e Å −3 Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.